Surfboard Design | Single & Single to Double Concaves

NATURAL CURVES SURFBOARDS

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Surfing & Media

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	SINGLE and SINGLE to DOUBLE CONCAVES

	May 1, 2019 Updated June 6, 2024

	Surfers are familiar with the common concave bottom contours in contemporary shortboards. The most common concave arrays are single concave and single to double concave. Concave shapes have more curve in the rail line than in the bottom. The curve in the rail rocker drops below the curve in the bottom rocker. This intriguing and nuanced juxtaposition of curves creates concaves. Concaves increase the surface are of the bottom of a board and amplify laminar flow. When tuned correctly these features generate lift, reduce drag, and amplify control.

	Note the RAIL ROCKER displayed in red drops below the BOTTOM ROCKER displayed in blue between the entry and the wide point to near the tail and rises above the bottom rocker near the nose and tail. This juxtapostion of the two curves creates the concave area in the bottom contours mid board and some vee behind the fins and in the nose.

	SINGLE CONCAVES SINGLE CONCAVES offer the surfer acceleration, projection, speed, maneuverability and maximum control. Single concave designs are very powerful, fast, and loose. The simple clean rail to rail arc of a single concave offers maximum controlled lift to the rails. Water flows in a smooth arc from rail to rail in single concaves enabling powerful, stable, and predictable turns. The smooth rail to rail water flow enables maximum controlled power through turns and nuanced turning radii for a wide variety of turns in different waves. Single concaves offer maximum control and maneuverability in critical barreling waves. Surfers can turn with maximum load off the bottom contours and rails. Occasionally, a single concave will have a touch of double concave or vee in the last 4" to 5" of the tail. This short double concave adds an extra element of stability, control, and release. Moving this double concave feature forward in the bottom contours yields the classic single to double concave.

	SINGLE to DOUBLE CONCAVES SINGLE to DOUBLE CONCAVES offer, in addition to acceleration, speed, projection, and maneuverability, an extra element of lift to a board. As water flows from rail the to the spine of the double concave it creates additional lift in the center of the board. The spine along the center of a double concave sustains the flow of water down the length of the bottom of a board maximizing laminar flow and directional stability through turns. The peak and the depth of the spine of a double concave can be moved forward or back and deeper or shallower to fine tune manuverability and control. A tuned double concave provides notable lift and reduces drag. The spine of the double concave and the performance features it offers make the design a great bottom contour option for the full spectrum of waves and conditions.

	Concaves are a radical design feature. By their nature they include conflicting forces. When well designed and balanced with other design variables and surfed with correct technique they generate lift and reduce drag. They offer acceleration, projection, planning speed, maneuverability, and control - all depending on nuanced and balanced design and surfer input. When poorly designed or not balanced with other design variables and surfed without correct technique they lack lift and will drag compromising all performance features. Concaves have different configurations, different depths, and different placement in a shape. Their radical nature allows surfers and shapers to tune performance by their configuration. A well designed concave array maximizes concaves' positive features - acceleration, projection, planning speed, maneuverability, and control.

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